1. Field of the Invention
The present invention is directed to an indicator for use with a projected beam employing a plurality of intersecting planes of light to obtain the indication.
2. Description of the Prior Art
Radiation therapy utilizes a beam of high energy radiation from a radiation source, such as a cobalt 60 supply or a linear accelerator. The portion of the patient to be treated is placed in the beam for a predetermined exposure time to obtain the desired therapeutic effect.
The radiation beam must be accurately positioned to ensure maximum benefit to the patient while minimizing undesirable side effects. Since the radiation beam is not visible to the human eye, various targeting devices have been utilized to ensure that the beam will impinge the correct portion of the patient. Typically, a target is placed on the patient's skin at the area to be treated. A light pattern, aligned with the path of the radiation beam, is positioned so that the light pattern is aligned with the target. The light pattern is then removed and the radiation beam established.
However, such a technique is often less than completely satisfactory. If the patient moves, for example, rolls about an axis normal to the radiation beam, diseased tissue within the body may move substantially out of the radiation beam but little misalignment can be noted. Even if the target and light pattern remain present during irradiation, the misalignment may not be detected. Under these circumstances, the effectiveness of the treatment may be substantially reduced.
Further, it is often necessary to ascertain the point at which the radiation beam exits the patient to insure that the patient and/or equipment are in proper alignment. Heretofore, a light has been mounted on the radiation source apparatus under the patient in opposition to the radiation beam to shine on the patient and mark the exit point of the radiation beam. However to properly position the light for all orientations of the radiation source is both expensive and awkward. In many cases, it restricts access to the patient by the medical personnel, preventing him/her from properly aligning the patient. The light is subject to damage from other equipment such as the patient bed.
The same concerns which apply to radiation therapy are also applicable to radiological diagnosis. That is, if the X-ray film sheet, patient and radiation beam are not properly positioned with respect to each other, the desired X-ray image on the film may not be obtained, requiring the X-ray to be taken over again and exposing the patient to additional radiation.